This protocol describes the method of measuring light environment using light sensitive films.
The light sensitive film (Optleaf, Taisei E&L, Tokyo, Japan) fades and changes the transmittance of light in proportion to the amount of accumulated light absorbed, with maximum absorption wavelength of 521 nm. The applicability and limitation of using this film are probably similar to those of traditional diazo paper methods (Friend 1961, Bardon et al. 1995), although effects of sunflecks have not been evaluated so far. Because of the simple methodology, various recent studies have used this film to investigate light environment (Hikosaka et al. 2001, Osada et al. 2001, 2002, Osada et al. 2004a, Osada et al. 2004b, Onoda et al. 2007, Osada et al. 2010).
- Film Optleaf R-3D (Taisei E&L, Tokyo, Japan; 35 mm in width and 10 m in length)
- A portable spectrometerD-meter RYO-470 (Taisei E&L, Tokyo, Japan) (or other spectrophotometers)
Step 1 Cut the film and write sequential number by waterproof pen at the edge of film pieces to distinguish each piece
Step 2 Measure initial value of light transmittance for each piece of film by the portable spectrometer
Step 3 Keep the film pieces in dark places (such as in small envelopes) until measurements
Step 4 Attach the film pieces on the surface of individual leaves (or places of measurements) by using clips, staples, or double-sided adhesive tapes (Fig. 1)
Step 5 Check the number of film pieces and their positions, i.e. which piece was set to each position of measurement
Step 6 At the same time, several film pieces and quantum sensors with data loggers are set at the positions of various light environments (from open places to shaded places) to construct calibration equation
Step 7 Wait about 3-7 days, depending on climate, ambient temperature, and light environments
Step 8 Collect the film pieces and quantum sensors, and keep the pieces in dark places such as in small envelopes, and bring them back to the lab
Step 9 Measure final values of light transmittance for each film piece
Step 10 Calculate fading rates of films from light transmittance before and after exposure
Step 11 Construct calibration equation to estimate photon flux density from the fading rate of films (Fig. 2)
Fig. 1. An example picture for measuring light microenvironment of individual leaves of Fagus japonica by using light sensitive films.
Fig. 2. Calibration lines to estimate PFD from fading rate of the film. The lines differ significantly between summer and winter in Kyoto, Japan (summer, r = 0.99; winter, r = 0.98).
Taisei E&L, Tokyo, Japan
TEL +81-3-3691-3112, FAX +81-3-3691-3035
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